Officer Darren Wilson is pictured in this undated handout evidence photo from the August 9 Ferguson Police shooting of Michael Brown in Ferguson, Missouri, released by the St. Louis County Prosecutor's Office on November 24, 2014. [Photo/Agencies]

FERGUSON, Mo.- The white police officer who shot and killed an unarmed black teenager in Ferguson, Missouri, in August got no severance deal when he resigned from the force, the mayor of the St. Louis suburb said on Sunday.

The officer, Darren Wilson, announced his resignation late Saturday, saying he feared for his own safety and that of his fellow police officers after a grand jury decided not to indict him in the fatal Aug 9 shooting of 18-year-old Michael Brown.

"There will be no severance or extension of benefits for Darren Wilson following his resignation," Mayor James Knowles told a news conference. Knowles also outlined new incentives to bring more African-Americans into the Ferguson police force.

Brown's death galvanized critics of the way police and the criminal justice system treat African-Americans and other minority groups. Protests in Ferguson have taken place for months and erupted into violence when the grand jury decided last Monday not to charge Wilson.

The protests have spread around the country. Over the past week there have been demonstrations in more than 100 cities, on public roadways, in shopping malls, and government buildings.

On Sunday, demonstrators temporarily shut down part of the busy Interstate 395 highway that runs through Washington, D.C., police said. The protest lasted less than an hour while people formed a human chain to block traffic in both directions.

Anger spilled onto the playing field when the NFL's St. Louis Rams played Oakland at home on Sunday. Some of the Rams entered the stadium with their hands raised overhead in a show of solidarity with Brown, who some witnesses say had his hands in the air when Wilson fired the fatal shots.

The St. Louis Police Officers Association said in a statement it was "profoundly disappointed" by the act.

"(They) chose to ignore the mountains of evidence released from the ... Grand Jury this week and engage in a display that police officers around the nation found tasteless, offensive and inflammatory," the statement said of the Rams players.

About 40 or 50 protesters briefly blocked a street outside Edward Jones Dome in downtown St. Louis after the game and later marched through the surrounding streets chanting "black lives matter."

Many Rams fans, mostly white men, applauded riot police as they followed the demonstrators. A handful of demonstrators were seen being taken into custody.